A fairly straightforward puzzle if you could get on its likeable and humorous wavelength. I mostly did, with a few caveats: a careless WATCHWORD as my FOI left me puzzling about how my LOI 1dn could possibly be WIPED, and likewise I'd bunged in OFF-THE-CUFF for 13dn after starting in on ODD-MAN-OUT which obviously was on a hiding to nothing. Third time lucky though!

My COD was 7dn once I realised that it really was talking about two *different* types of flight - I'd only needed the stairsy type to enter it on my first pass.

Many thanks to the setter: have a good weekend, everybody!

ACROSS
1 Crowd chat conjured up in slogan (9)
CATCHWORD - (CROWD CHAT*) ["conjured up"]

6 Odd bits of grub given to prisoner in his camp? (5)
GULAG - G{r}U{b} given to LAG [prisoner]

9 Something freely given? That is taken by force (7)
PRESSIE - I.E. [this is], taken by PRESS [force]

10 Line written by church composer is ghastly (7)
CHARNEL - L [line] written by CH ARNE [church | composer]

11 Franchise needing guidance when two characters have swapped positions (10)
DEALERSHIP - swap two characters in LEADERSHIP [guidance]

12 Illustration rendered by ace printing unit (4)
PICA - PIC [illustration] rendered by A [ace]

14 Daggers the Spanish brought into form of evil magic? (5)
OBELI - EL [the (Spanish)] brought into OBI [form of evil magic]

15 Dispute involving four dukes? (9)
FISTFIGHT - cryptic def, a "duke" being a fist

16 Advice to man with cat in performance, leading to a benefit (4,5)
TURN AGAIN - TURN [performance], leading to A GAIN [a | benefit].
"Turn again, Dick Whittington, thrice Mayor of London..."

18 Irritable computer whizz? (5)
TECHY - double def, though I'd normally spell one of these "tetchy" myself...

20 Aim of mountaineers? Not all of them came back (4)
ACME - hidden reversed in {th}EM CA{me}

21 The French male wearing false hair and dress shows a bit of freedom (6,4)
WIGGLE ROOM - LE [the (French, male)] wearing WIG + GROOM [false hair + dress]

25 Nothing in Italian city, little good for holiday activity? (7)
TOURING - O [nothing] in TURIN [Italian city] + G ["little" good]

26 What has cups next to stinking bottle? (7)
BRAVERY - BRA [what has cups] next to VERY [stinking, as in "stinking rich" I guess]

27 Dirty job involving spades (5)
DUSTY - DUTY [job] involving S [spades]

28 One club maybe for a bachelor? (9)
SINGLETON - double def. A singleton is the holding of one card of a suit in Bridge.

DOWN
1 Made the grade as a priest in ceremony? (5)
COPED - double def. A priest in a ceremony may be wearing a cope.

2 Adolescent as a born troublemaker originally, growing up (7)
TEENAGE - reverse all of E.G. A NEE [as | a | born] + T{roublemaker}

3 Very funny chair with style ill conceived (10)
HYSTERICAL - (CHAIR + STYLE*) ["ill conceived"]

4 Maidens perhaps seen as headless sweethearts (5)
OVERS - {l}OVERS ["headless" sweethearts]. Cricketing maidens, that would be.

5 Emily? Endlessly unsteady, having got thus in pub (9)
DICKINSON - DICK{y} ["endlessly" unsteady] + SO [thus] in INN [pub]

6 Learner in school dressed to attract? (4)
GLAM - L [learner] in GAM [school].
Well worth remembering both POD and GAM for school in these parts.

7 What comes at end of different flights (7)
LANDING - cryptic def. Flights as in stairs, or voyages by plane: both end in landings!

8 Courage of everyone imprisoned in tower (9)
GALLANTRY - ALL [everyone] imprisoned in GANTRY [tower]

13 Unconventional, like a newly escaped convict? (3-3-4)
OFF-THE-WALL - a (very!) newly escaped convict may have just jumped down from the prison wall.

14 Old statue, after renovation, survived (9)
OUTLASTED - (OLD STATUE*) ["after renovation"]

15 Ruddy huge birds (9)
FLAMINGOS - FLAMING OS [ruddy | huge (as in outsize)]

17 Gossip is associated with us after hard drink (7)
RUMOURS - OURS [associated with us] after RUM [hard drink]

19 Most stuffy little room in which son hides (7)
CLOSEST - CLOSET [little room] in which S [son] hides

22 Bigwig with silver set up in the country (5)
GABON - reverse all of NOB + AG [bigwig + silver]

23 A Yankee probing fellow of a bygone civilisation (5)
MAYAN - A Y probing MAN [fellow]

24 Ruth affected by pockmarks, we hear? (4)
PITY - homophone of PITTY [pockmarked]